2.1 Study sites
Plateau
pikas can live in various habitats with different soil types,
topographies, and microclimates. To identify a general pattern of how
plateau pika disturbance influences the ecosystem services of alpine
grasslands, this study selected five sites with different alpine
grassland types, topographies and microclimates as field survey areas.
These five survey sites have a similar typical plateau continental
climate, with mean annual temperatures of 3.3℃ in Luqu
(102°10´-102°52´E, 34°16´-34°37´N), 2.0℃ in Gangcha (99°53´-100°36´E,
37°17´-37°29´N), 2.0℃ in Haiyan (100°37´-100°58´E, 36°51´-37°14´N), 2.1℃
in Qilian (99°28´-100°54´E, 37°58´-38°27´N), and 3.7℃ in Gonghe
(99°41´-100°12´E, 36°21´-36°36´N). These survey areas range in elevation
from 3000 m at the Gangcha survey site to 3550 m at the Luqu survey
site, with average annual precipitation varying from 350 mm at the
Gonghe survey site to 630 mm at the Luqu survey site. According to the
Chinese soil classification system (Gong, 2001), the soil type is alpine
meadow soil in the five survey sites, similar to Cambisol in the WRB
soil classification system. Soil nutrients are different among the five
survey site areas (Pang et al., 2020a, 2020b).
The five field survey areas were placed in cold-season areas, which were
fenced from mid-April to September, and fences were opened to grazing
yaks with a 3.4 yaks ha-1 grazing stock rate from
mid-October to early April (Zhang et al., 2020). The alpine grasslands
in the five survey areas were dominated by Kobresia humilis andKobresia pygmaea . Plateau pikas were the only small burrowing
herbivores in the field survey areas, and their population generally
peaked in August (Pang et al., 2020a, 2020b; Qu et al., 2013), implying
that sampling
plants
and soil in August may best reflect the effect of plateau pika
disturbance on alpine grassland ecosystem services.